Artificial shark skin boosts swimming speeds

Harvard researchers have used 3-D printing to create artificial shark skin, an advance that can help unlock the secret behind the marine predator's speed and agility under the waves.
In tests, the artificial shark skin boosted swimming speeds by up to 6.6 per cent, researchers found.
Shark skin is composed of microscopic toothlike scales, called denticles. These tiny bumps disrupt the flow of water as the animal swims, reducing drag, but scientists did not know exactly how this happens.
This is the first time that anyone has measured the swimming energy benefit of bumpy shark skin compared with smooth skin, said George Lauder, a biologist at Harvard University in Cambridge, Massachusetts, and co-author of the study.

The researchers found a mako shark in a local fish market and took a high-resolution scan of its skin surface. By zooming in on a single denticle, the team was able to create a computer model of shark skin made of thousands of denticles.
The team used a 3D printer to embed artificial scales into a flexible membrane, spending a year trying different materials to find ones that worked. They used a scanning electron micrograph to image the fake skin, 'LiveScience' reported.

The researchers then affixed the artificial skin to both sides of a flexible foil that was kept still or was made to flap like a swimming shark, and put it in a tank of flowing water.

Compared with the smooth foil alone, the foil with the artificial skin reduced drag by 8.7 per cent at the lowest water flow speeds.
At the highest flow speed, the fake skin actually produced 15 per cent more drag than the smooth surface did standing still, but when the researchers flapped the foil like a fish 1.5 times per second, the shark skin improved swimming speed by 6.6 per cent, using 5.9 per cent less energy.
The study was published in the Journal of Experimental Biology.